武汉地区1988~2002年植被覆盖度变化动态分析

植被是生态系统最重要的组成部分,而植被覆盖度是衡量地表植被状况的一个最重要的指标,是生态系统健康评价的前提和必要的基础。利用1988、1991、1996和2002年4个时相的TM和ETM+遥感影像为数据源,以归一化植被指数(NDVI)像元二分法为植被覆盖度估算模型,计算了武汉地区不同时期的植被覆盖度,生成了该地区不同时序的植被覆盖度图,以此分析武汉地区植被覆盖度的时空变化。结果表明,武汉地区在1988~2002年这14年,植被覆盖度变化明显,整个地区的平均植被覆盖度从58.41％下降到50.45％,下降值为7.96%,特别是江夏区和主城区变化幅度最为显著,下降值分别为9.98%和7.14%。植被覆盖度下降最快时间段是1996~2002年,恢复阶段是1991~1996年。从空间上来看,全地区都处于下降阶段,特别是郊区江夏区和市区,通过分析发现,这大部分原因都是城市发展的结果,导致了生态环境的恶性发展,值得各方面的注意。

Dynamic Analysis of Vegetation Fraction Change in Wuhan Region from 1988 to 2002

Vegetation includes all plant communities that cover the earth surface.And vegetation fraction is the most important index to scale the status of the vegetation of the region so the vegetation is the composition and the function body of ecological system.Vegetation fractions in different districts of Wuhan were calculated based on remote sensing images (TM images and ETM+ images) in 1988,1991,1996 and 2002 by employing   method for dimidiate pixel model,and the vegetation fraction maps of different periods were generated to analysis the temporal change of vegetation fraction of Wuhan area.The results showed that,the vegetation fraction changed much from 1988 to 2002; the average vegetation fraction of the whole area was decreased from 58.41% to 50.45%,especially in Jiangxia district and the central district.From 1996 to 2002 is the period which vegetation fraction decreased the most sharply in this period.From 1991 to 1996 the vegetation fraction was lightly increased in the whole study area.Analyzing spatial changing characteristics in the whole study area we can see that,the whole area was in the decreasing moment,especially in Jiangxia district and the central district,this was the result of urban development,and led to the malign development of the environment,worthy of all aspects of attention.